1. Field of the Invention
The present invention relates generally to an inflating device, and more particularly to an inflating device switched between a small pump unit and a large pump unit for optionally inflating an inflatable article.
2. The Prior Arts
As we all know, an inflating device is widely used in our daily life for inflating an inflatable article, like a tire of a bicycle, motorbike and a basket ball, thereby providing much convenience to the people. Before the inflatable article is inflated by the conventional inflating device, the inflatable article is in an entirely flat condition and has low internal pressure, a large pump unit should be applied since the same can provide large air flow into the inflatable article and is subject to small air resistance from the inflatable article, so that the inflatable article can be quickly inflated. When the inflatable article is nearly full, has high internal pressure and is inflated continuously by the large pump unit, the large pump unit is subject to high air resistance from the inflatable article and difficult to inflate the inflatable article. When the inflatable article is nearly full and has high internal pressure, a small pump unit should be applied since the same provide small air flow into the inflatable article and is subject to small air resistance from the inflatable article and easy to inflate the inflatable article. In other words, large and small pump units are needed to facilitate inflation of an inflatable article and are beneficial that an inflating device possesses these large and small pump units at the same time. However, the conventional inflating device provides only a constant injection pressure, either large or small injection pressure.